Method and device for controlling a drive unit of a vehicle

The present invention relates to methods and devices for controlling a drive unit of a vehicle.

German Published Patent Application No. 199 28 477 describes a method and a device for controlling a drive unit of a vehicle. In that document, starting from the comparison of a first acceleration variable, which is calculated at least starting from the operating state of the drive unit, and a second acceleration variable, an error is detected in the field of fuel metering. The second acceleration variable is recorded using an acceleration sensor which directly detects the vehicle acceleration.

Furthermore, German Published Patent Application No. 103 15 410 describes a method and a device in which, starting from the desired torque and the actual torque of the internal combustion engine that is calculated starting from the operating state of the internal combustion engine, errors are detected.

The disadvantage in both of the foregoing methods is that an accurate monitoring is possible only at very high expenditure. An accurate calculation of the actual torques, starting from operating states such as the injected fuel quantity and the rotational speed, is very costly. This applies particularly to modern internal combustion engines, that have an exhaust gas aftertreatment system, in which not the entire fuel quantity is converted into torque, but in which a part of the injected fuel quantity is required for the exhaust gas aftertreatment. In such systems, the expenditure rises greatly, especially within the scope of the application. That is, various characteristics maps and characteristic quantities have to be recorded for each individual vehicle, and stored.

Because the second acceleration variable includes a first component in the direction of the vehicle longitudinal axis, and a second component perpendicular to the vehicle longitudinal axis, a substantially more accurate and simpler monitoring is possible. Because one component perpendicular to the vehicle axis is taken into consideration, uphill and downhill travel can certainly be detected, and a correspondingly accurate acceleration value can be determined. This means that the second acceleration variable is used for detecting the operating state. The second acceleration variable is used as second operating state, or rather, the operating state is detected starting from the second acceleration variable.

The second acceleration variable may be measured using a suitable sensor. Such acceleration sensors are available inexpensively. Corresponding acceleration sensors are used, for instance, in other systems, such as in an ABS system or an ESP system. These sensors supply acceleration variables having several components. They particularly have a component in the direction of the vehicle longitudinal axis and in the direction perpendicular to the vehicle longitudinal axis.

A simple sensor may be used which only records the acceleration in the vehicle longitudinal axis, and the second component is calculated using other variables. For example, the second component can be ascertained in a simple manner using an inclination sensor. Alternatively, it may also be provided that a corresponding value is derived from a signal which characterizes the atmospheric pressure and/or the atmospheric pressure change, or from a GPS signal.

The vehicle\'s mass may be used for determining the first acceleration variable, since it has a substantial influence on the acceleration.

At least the variable characterizing the injected fuel quantity may be taken into consideration as the operating state of the drive unit. Such a variable that characterizes the injected fuel quantity is, for example, the duration of activation of a control element or the angle the crankshaft and/or the camshaft sweeps over during the activation. Besides these variables, other variables characterizing the injected fuel quantity can also be used, which may be present internally in the control unit.

A fixed vehicle mass may be assumed. A substantial improvement of the monitoring comes about if in each case the current vehicle mass is ascertained and used for the monitoring. In certain operating states, the vehicle mass may be calculated at least starting from the vehicle-specific characteristic variables and the acceleration.

Using the method described and the procedure described, it is possible to have direct monitoring of the vehicle for undesired accelerations. Using the method, one obtains a clear reduction in the complexity of the monitoring of the control unit, and this applies particularly for functional monitoring. Development times and application times and costs are clearly reduced and, at the same time, reliability and accuracy can clearly be increased. The method according to example embodiments of the present invention is independent of the combustion method and the type of drive, and can therefore be used for all drives of vehicles, such as especially Diesel vehicles, gasoline engines, electric drives and hybrid drives.

Exemplary embodiments of the present invention are shown in the drawings and are explained in more detail in the following description.